Drug delivery to the respiratory tract using dry powder inhalers

Engineered mannitol as an alternative carrier to enhance deep lung penetration of salbutamol sulphate from dry powder inhaler

In this research mannitol particles were prepared by recrystallisation using non-solvent precipitation technique to investigate the effect of engineered carrier particles on their physicochemical properties and the in vitro deposition profiles of a model drug (salbutamol sulphate (SS)) from a dry powder inhaler (DPI). To this end, mannitol aqueous solution (15%, w/v) was added to different ratios of ethanol:water (100:0, 95:5, 90:10 and 85:15) to obtain mannitol particles. These crystallised mannitol particles were analysed in terms of micromeritic properties, morphology, DSC, FT-IR, and in vitro fine particle fraction (FPF) and emitted dose (ED) of SS. The results showed that the elongation ratio of all the recrystallised mannitol batches was higher than the original material giving them a needle-shaped morphology. Salbutamol sulphate deposition profiles from DPI formulation containing recrystallised needle-shaped mannitol showed enhanced performance and better delivery to the lower MSLI stages. The FPF increased from 15.4+/-1.1 to 45.8+/-0.7% when the commercial mannitol was replaced by mannitol crystallised from ethanol:water (90:10). This improvement could be due to the presence of elongated mannitol crystals in formulation blends. Solid state characterisation of engineered mannitol showed that the commercial mannitol was beta-form, mannitol recrystallised from ethanol:water (85:15) was alpha-form and that samples recrystallised in presence of pure ethanol or other ratios of ethanol:water (95:5 and 90:10) were the mixtures of alpha-, beta- and delta-forms. Multi-solvent recrystallisation technique was proved to have potential to produce mannitol crystals suitable for enhanced aerosolisation efficiency. Comparing different crystallised mannitol formulations showed that the final form (the type of polymorph) of the crystallised mannitol does not have a substantial effect on salbutamol sulphate aerosolisation performance.

Monitoring safety of liposomes containing rifampicin on respiratory cell lines and in vitro efficacy against Mycobacterium bovis in alveolar macrophages

Rifampicin-encapsulated liposome suspensions were prepared by a chloroform-film method and converted to dry powders by freeze-drying with mannitol as a cryoprotectant. The liposome suspension had multilamellar nanovesicles with 50% rifampicin encapsulation. The liposome dry powder comprised particles with a mass median aerodynamic diameter of 3.4 mum, with 60% present as a fine particle fraction. Rifampicin-encapsulated liposomes were evidently nontoxic to respiratory associated cells, including bronchial epithelial cells, small airway epithelial and alveolar macrophages (AMs). Furthermore, the liposomes did not activate AMs to produce interleukin-1 beta, tumor necrosis factor-alpha, and nitric oxide at a level that would cascade to other inflammatory effects. The minimum inhibitory concentrations against Mycobacterium bovis was 0.2 and 0.8 microM for liposomes containing rifampicin and free rifampicin, respectively. The less negatively charged reconstituted liposome displayed the greatest activity against intracellular growth of M. bovis.

Influence of fines on the surface energy heterogeneity of lactose for pulmonary drug delivery

The effects of the blending of lactose fines to the overall adhesion property of coarse alpha-lactose monohydrate carrier particles were investigated. Five samples, three of them commercial samples from DOMO (Lactohale) LH100, LH210, and LH250) whilst the other two are blends of LH210 and LH250, were studied. Characterisation included particle sizing, SEM, PXRD and IGC. Dispersive surface energy gamma(SV)(d) was determined using a finite concentration IGC method to obtain a distribution profile. The gamma(SV)(d) distribution of lactose crystals was found to vary from 40 to 48mJ/m(2). The unmilled coarse crystalline lactose sample (LH100) gamma(SV)(d) was lowest and showed less heterogeneity than the milled sample (LH250). Fines (LH210) were found to have the highest gamma(SV)(d) value. The samples with loaded LH210 were found to have a higher energy than LH100. The amount of LH210 in Blend 1 was not able to decrease surface energy heterogeneity, whereas sample Blend 2 showed adequate loading of fines to obtain a relatively homogeneous surface. Addition of fines resulted in an increase in gamma(SV)(d), suggesting that coarse lactose surfaces were replaced by surfaces of the fines. Increasing the loading of fines may result in a more homogeneous surface energy of lactose particles.

Continued Investigation Into the Influence of Loaded Dose on the Performance of Dry Powder Inhalers: Surface Smoothing Effects

The aerosolization of salbutamol sulfate, measured as fine particle dose (FPD LD) and fine particle fraction (FPF LD) (<6.4 microm mass median aerodynamic diameter), from two sieved (63-90 microm) lactose monohydrate carriers, one as supplied, one smoothed by controlled surface dissolution, was studied. In general, no significant variation in FPD LD was observed at drug loadings between 10 and 63.5 microg and 10 and 135 microg for the surface dissolved and as supplied lactose monohydrates, respectively. Increasing the drug load above these levels resulted in linear increases in FPD LD with increasing drug load with the surface dissolved lactose monohydrate exhibiting higher FPD LD and FPF LD. This suggests that, at lower drug loadings, areas of the carrier exhibiting higher adhesion, so-called active sites, were being preferentially occupied and filled. Since there was no evidence of drug agglomeration using scanning electron microscopy, the observations suggest that the number and range of such higher energy "active sites" can be reduced by modifying the surface roughness, that is, energies, of the carrier.

Dry powder inhalers (DPIs)--a review of device reliability and innovation

A wide range of dry powder inhaler (DPI) devices are currently available on the market to deliver drugs into lungs with a view to maximise drug delivery with low variability. DPIs also face numerous clinical challenges, particularly related to variable patient factors such as age, clinical condition and inspiratory flow. Due to the drug formulation and the design of devices, different DPIs do not show the same performance and manufacturers are taking a variety of device design approaches. The characteristics of an ideal DPI, recent innovations in powder formulation and device design are not universally reliable in terms of dose variability, clinical efficacy, user friendliness and economy. This mini review examines whether device reliability is more important than innovation. This study enables a comparison of the relative merits of optimising existing DPIs or seeking to develop novel devices.

Application of supercritical fluid to preparation of powders of high-molecular weight drugs for inhalation

The application of supercritical carbon dioxide to particle design has recently emerged as a promising way to produce powders of macromolecules such as proteins and genes. Recently, an insulin powder for inhalation was approved by authorities in Europe and the USA. Other macromolecules for inhalation therapy will follow. In the 1990s proteins were precipitated with supercritical CO(2) from solutions in an organic solvent such as dimethylsulfoxide, which caused significant unfolding of protein. Since 2000, aqueous solutions of proteins and genes have generally been used with a cosolvent such as ethanol to precipitate in CO(2). Operating conditions such as temperature, pressure, flow rates, and concentration of ingredients affect the particle size and integrity of proteins or genes. By optimizing these conditions, the precipitation of proteins and genes with supercritical CO(2) is a promising way to produce protein and gene particles for inhalation.

Preparation and physicochemical characterization of supercritically dried insulin-loaded microparticles for pulmonary delivery

In the search for non-invasive delivery options for the increasing number of therapeutic proteins, pulmonary administration is an attractive route. Supercritical fluid (SCF) drying processes offer the possibility to produce dry protein formulations suitable for inhalation. In this study, insulin-loaded microparticles suitable for pulmonary administration were prepared and characterized. N-Trimethyl chitosan (TMC), a polymeric mucoadhesive absorption enhancer and dextran, a non-permeation enhancer, were used as carriers for insulin. The particles were prepared by spraying an acidic water/DMSO solution of insulin and polymer into supercritical carbon dioxide. The mean size of the particles was 6-10microm (laser diffraction analysis) and their volume median aerodynamic diameter ca. 4microm (time-of-flight analysis). The particles had a water content of ca. 4% (w/w) (Karl-Fischer), and neither collapsed nor aggregated after preparation and storage. In the freshly prepared dried insulin powders, no insulin degradation products were detected by HPLC and GPC. Moreover, the secondary and tertiary structures of insulin as determined by circular dichroism and fluorescence spectroscopy were preserved in all formulations. After one-year storage at 4 degrees C, the particle characteristics were maintained and the insulin structure was largely preserved in the TMC powders. In conclusion, SCF drying is a promising, protein-friendly technique for the preparation of inhalable insulin-loaded particles.

Study of the RESS process for producing beclomethasone-17,21-dipropionate particles suitable for pulmonary delivery

The purpose of this research was to micronize beclomethasone-17,21-dipropionate (BDP), an anti-inflammatory inhaled corticosteroid commonly used to treat asthma, using the rapid expansion of supercritical solution (RESS) technique. The RESS technique was chosen for its ability to produce both micron particles of high purity for inhalation, and submicron/nano particles as a powder handling aid for use in next generation dry powder inhalers (DPIs). Particle formation experiments were carried out with a capillary RESS system to determine the effect of experimental conditions on the particle size distribution (PSD). The results indicated that the RESS process conditions strongly influenced the particle size and morphology; with the BDP mean particle size decreasing to sub-micron and nanometer dimensions. An increase in the following parameters, i.e. nozzle diameter, BDP mol fraction, system pressure, and system temperature; led to larger particle sizes. Aerodynamic diameters were estimated from the SEM data using three separate relations, which showed that the RESS technique is promising to produce particles suitable for pulmonary delivery.

Characterization and aerodynamic evaluation of spray dried recombinant human growth hormone using protein stabilizing agents

The effect of the protein stabilizers on the stability and aerosol performance of spray dried recombinant human growth hormone (SD rhGH) was investigated. rhGH solution was spray dried alone, with polysorbate 20 (at three concentrations of 0.05%, 0.01%, and 0.005%), Zn(2+) (by Zn(2+):rhGH molar ratio of 2:1 and 4:1), and/or lactose (by lactose:rhGH weight ratio of 2:1). Size exclusion chromatography (SEC) analysis of spray dried powders demonstrated that of all the potential protein stabilizers, the combination of polysorbate 20 (0.05%), Zn(2+) (Zn(2+):rhGH molar ratio of 2:1) and lactose (lactose:rhGH weight ratio of 2:1) was the most effective at protecting rhGH against aggregation during spray drying. The results of circular dichroism (CD) analysis revealed that using of polysorbate 20 (in all concentrations) and Zn(2+) (by Zn(2+):rhGH molar ratio of 2:1) together in the formulations would preserve rhGH conformational stability during the process. The particle size distribution data obtained by laser diffraction method showed all SD rhGH formulations had volume median diameter and mean diameter below 5mum. The characterization of the aerosol performance of the spray dried powders by Andersen cascade impactor (ACI) showed that by increasing the concentration of polysorbate 20 in the formulations the aerodynamic efficiency of the resultant particles was reduced. In conclusion, the optimum amounts of polysorbate 20, Zn(2+) and lactose satisfied both physical stability during spray drying process (2.37% aggregation) and good aerosol performance (fine particle fraction; FPF=38.52%).

Physical characteristics and aerosolization performance of insulin dry powders for inhalation prepared by a spray drying method

The objective of this study was to investigate the influence of formulation excipients on the physical characteristics and aerosolization performance of insulin dry powders for inhalation. Insulin dry powders were prepared by a spray drying technique using excipients such as sugars (trehalose, lactose and dextran), mannitol and amino acids (L-leucine, glycine and threonine). High performance liquid chromatography and the mouse blood glucose method were used for determination of the insulin content. The powder properties were determined and compared by scanning electron microscopy, thermo-gravimetric analysis and size distribution analysis by a time-of-flight technique. The in-vitro aerosolization behaviour of the powders was assessed with an Aerolizer inhaler using a twin-stage impinger. Powder yield and moisture absorption were also determined. Results showed that there was no noticeable change in insulin content in any of the formulations by both assay methods. All powders were highly wrinkled, with median aerodynamic diameters of 2-4 microm, and consequently suitable for pulmonary administration. The tapped density was reduced dramatically when glycine was added. The powders containing mannitol, with or without L-leucine, were less sensitive to moisture. The highest respirable fraction of 67.3 +/- 1.3% was obtained with the formulation containing L-leucine, in contrast to formulations containing glycine and threonine, which had a respirable fraction of 11.2 +/- 3.9% and 23.5 +/- 2.5%, respectively. In addition, powders with good physical properties were achieved by the combination of insulin and trehalose. This study suggests that L-leucine could be used to enhance the aerosolization behaviour of the insulin dry powders for inhalation, and trehalose could potentially be used as an excipient in the formulations.

Promising ternary dry powder inhaler formulations of cromolyn sodium: formulation and in vitro-in vivo evaluation

Glucose monohydrate and sorbitol were evaluated as alternative carriers to á-lactose monohydrate in dry powder inhalations. Cromolyn sodium (CS) - carrier binary formulae were prepared and tested in vitro by aerosolization via a twin stage impinger using three types of inhaler devices; Spinhaler, Aerolizer and Handihaler. Glucose monohydrate and sorbitol-containing formulae that were inhaled via a Handihaler showed significantly higher drug fine particle fractions (P<0.001) than that of the same formulae aerosolized via other devices. Upon storage of the prepared formulae under uncontrolled humidity, that may be encountered during storage and use, marked reductions in these fractions were observed. Incorporation of an optimum Aerosil 200 concentration, as a ternary component, minimized this effect. A urinary excretion pharmacokinetic method was used to evaluate the bioavailability of the selected ternary formulae, inhaled via a Handihaler, relative to the marketed Intal Spincaps, inhaled via a Spinhaler. It was found that the relative bioavailability percentages of the developed formulae were more than twice that of the marketed one suggesting possible future utilization of these more effective ternrry formulae using the more efficient Handihaler inhaler device.

Peak inspiratory flow rates generated through the Novolizer and the Turbuhaler dry powder inhaler devices by children with stable asthma

We compared the peak inspiratory flows (PIF) generated through a novel dry powder inhaler device, the Novolizer (PIF-N), and the Turbuhaler (PIF-T). Forty-six pediatric patients with stable bronchial asthma were randomized in an open-label, multicenter, crossover trial. No drug was administered during the inhalation maneuvers that were spaced by 10 min. There was neither a carryover nor a sequence effect. The patients were characterized by mean age of 8.5 years, mean FEV(1) of 1.79 L, and mean PIF without any device (baseline, PIF-B) of 185 L/min. Through the devices mean PIF-N of 94 L/min and mean PIF-T of 69 L/min were achieved, calculated from the maxima of three inhalations. This resulted in p < 0.0001 for the difference. The median PIFN/PIF-T ratio was estimated as 1.39. Each child achieved a higher PIF-N than PIF-T and was able to release the feedback mechanisms of the Novolizer indicating sufficient inhalation performance. We conclude that the PIF through the Novolizer is higher than the PIF through the Turbuhaler in stable asthmatic children. The flow rates achieved through the Novolizer allow for sufficient lung deposition even in children as young as 6 years.

Investigation of triboelectric charging in dry powder inhalers using electrical low pressure impactor (ELPI™)

Electrostatics and triboelectrification phenomena in dry powder inhalers (DPI) are not well understood, but as shown in this study they may play an important role. Using model formulations of albuterol in lactose, the extent of triboelectrification in the operation of DPI was investigated using an electrical low pressure impactor (ELPI). An experimental apparatus was developed, the performance of the ELPI was evaluated for consistency and reproducibility, and compared to a conventional inertial impactor. Using a statistical experimental design the effects of lactose type, drug load, capsule fill, capsule material, and inhaler were assessed. DPI formulations appear to be subject to strong triboelectric effects. Charge separation can occur between different size fractions, i.e. different fractions can carry charges of different sign. In particular, lactose type, inhaler, and capsule material have a strong effect on the magnitude and polarity of the charge developed during DPI operation. The study suggests that the polarity of the aerosol can be controlled by choice of lactose type, capsule material, and inhaler, which could be exploited for targeting different lung physiologies.

Pharmacokinetics of inhaled monodisperse beclomethasone as a function of particle size

AIMS

For optimal efficacy, antiasthma drugs should be delivered to the desired region in the airways. To date, the optimal particle size for steroids in adults is not known. The aim of the study was to evaluate the pulmonary bioavailability for inhaled beclomethasone dipropionate (BDP) aerosols of different particle sizes.

METHODS

In a randomized single-blind crossover trial, 10 mild asthmatic patients inhaled monodisperse BDP aerosols with mass median aerodynamic diameters (MMADs) of 1.5, 2.5 and 4.5 microm. Gastrointestinal absorption was blocked by activated charcoal. Plasma concentrations of 17-beclomethasone monopropionate (17-BMP) were measured by liquid chromatography plus mass spectrometry.

RESULTS

Aerosols with MMADs of 1.5 microm, 2.5 microm, and 4.5 microm gave mean maximum concentrations (C(max)) of 17-BMP of 475 pg ml(-1), 1300 pg ml(-1), and 1161 pg ml(-1), respectively. The area under the curve (AUC) values of 17-BMP for MMADs of 1.5 microm, 2.5 microm, and 4.5 microm were 825 pg ml(-1) h, 2629 pg ml(-1) h, and 2276 pg ml(-1) h, respectively. The mean terminal half-time of 17-BMP for all three aerosol sizes was around 1.5 h.

CONCLUSIONS

Monodisperse BDP aerosols with a MMAD of 1.5 microm gave two-three fold lower values for C(max) and AUC than those with MMADs of 2.5 and 4.5 microm.

Humidity-induced changes of the aerodynamic properties of dry powder aerosol formulations containing different carriers

This paper presents the findings of two related studies. The aim of the first was to study any changes in the aerodynamic properties of salbutamol base powder formulations when different sugars were used as the carriers, after storage at an elevated humidity (75% RH), and whether any such changes (if any) were related to the physical properties of the carriers. The aim of the second was to investigate whether "ageing", i.e. storage of the carrier, drug and blends under desiccation for more than 2 years, affected the aerodynamic properties of salbutamol sulphate powder formulations. Different formulations were prepared, each containing 1.5% (w/w) micronised salbutamol base or sulphate blended with the sieved fraction (63-90 microm) of one of the following sugars: alpha lactose monohydrate, sorbitol, maltose and dextrose. The salbutamol base blends were then stored unprotected at 75% RH (ambient temperature) and salbutamol fine particle fractions (FPFs) were measured by laser diffraction (LD) (% < 5.2 microm) and a multistage liquid impinger (MSLI) (% < 5.3 microm), following aerosolisation at 100 l min(-1) from a model glass inhaler, after storage of each formulation at the elevated conditions for 0, 1 and 6 days. Particle morphology and equilibrium moisture content (EMC) of each formulation prior to and after storage were also evaluated. However, the salbutamol sulphate blends containing either "fresh" or "aged" components were only characterized using LD at 60 l min(-1). Prior to exposure to 75% RH, the lactose blend was found to give the highest FPF of salbutamol (30% by LD and 37% by MSLI), followed by the sorbitol blend (17% by LD and 29% by MSLI), then by the dextrose blend (15% by LD and 25% by MSLI) and finally by the maltose blend (13% by LD and 13% by MSLI). Exposure to 75% RH for 6 days resulted in a small reduction of salbutamol FPF from the lactose blend but drastic diminution of salbutamol FPFs from other blends. After exposure to the high RH, the lactose blend adsorbed ca. 0.4% whilst each of the other sugars took up larger quantities of water (15-40%) and underwent a marked change in the surface texture of the particles. "Ageing" of the carriers and/or formulations did not seem to alter the aerodynamic properties of the drug. "Ageing" of micronised salbutamol sulphate prior to blending, however, was found to improve the FPF of drug. LD was capable of detecting subtle differences between the various formulations and generated FPF results that correlated with those measured by MSLI.

Applicability of an ultrasonic nebulization system for the airways delivery of beclomethasone dipropionate in a murine model of asthma

PURPOSE

We have assessed the use of an ultrasonic nebulization system (UNS), composed of ultrasonic nebulizer and diffusion dryer filled with charcoal, for the effective delivery of beclomethasone to the airways in a murine asthma model.

METHODS

Solution of beclomethasone in ethanol was aerosolized using an ultrasonic nebulizer. Passage of the aerosol through a drying column containing charcoal and deionizer produced dry beclomethasone particles. Particles were delivered to BALB/c mice placed in a whole-body exposition chamber 1 h before intranasal challenge with ovalbumine. Efficacy of beclomethasone delivery was evaluated by examining bronchoalveolar lavage fluid (BALF) cytology.

RESULTS

Effect of three UNS system parameters on aerosol particle size was investigated. The critical parameter affecting the size of dry particles was beclomethasone concentration in aerosolized solution and solution flow rate while power level of ultrasonic nebulizer generator had no effect. Administration of beclomethasone at calculated dose of 150 microg/kg to mice significantly decreased total cell number and relative eosinophil number in BALF.

CONCLUSIONS

The UNS system produces a monodisperse aerosol that can be used for inhalative delivery of poorly water soluble substances to experimental animals. The UNS system minimizes formulation requirements and allows rapid and relatively simple efficacy and toxicity testing in animals.

The effect of carrier surface treatment on drug particle detachment from crystalline carriers in adhesive mixtures for inhalation

In this study, the effect of lactose carrier surface treatment on drug particle detachment during inhalation has been investigated. Crystals of marketed brands of alpha lactose monohydrate brands normally exhibit a certain surface rugosity and contain natural fines and impurities on their surface, which influence the drug-to-carrier interaction in adhesive mixtures for inhalation. Submersion treatment may change these surface characteristics. Two different sieve fractions (63-90 and 250-355microm) were submerged in mixtures of ethanol and water (96 and 80% v/v, respectively). Microscopic observation and laser diffraction analysis revealed that neither the shape nor the size of the carrier particles was changed by the submersion treatment. However, the specific surface area and the amount of impurities appeared to decrease substantially after submersion, and the magnitude of the decrease was different for the different ethanol-water mixtures. The reduction in specific surface area was attributed particularly to the removal of the adhering lactose fines from the carrier surface. Mixtures with budesonide (in a wide range of carrier payloads) were prepared before and after treatment. Drug particle detachment from the various mixtures was studied with a sieve test and with a cascade impactor analysis at 30 and 60l/min. Two different types of inhalers were used, one generating lift- and drag-forces (ISF inhaler) and one generating inertial forces (test inhaler), respectively. The cascade impactor and sieve test experiments showed that an increase in carrier surface smoothness results in a reduced drug particle detachment during inhalation, which was independent of the type of inhaler used. This reduction could be attributed to the removal of the adhering lactose fines which may provide shelter for the drug particles from press-on forces during mixing.

Physicochemical and in vitro deposition properties of salbutamol sulphate/ipratropium bromide and salbutamol sulphate/excipient spray dried mixtures for use in dry powder inhalers

The physicochemical and aerodynamic properties of spray dried powders of the drug/drug mixture salbutamol sulphate/ipratropium bromide were investigated. The in vitro deposition properties of spray dried salbutamol sulphate and the spray dried drug/excipient mixtures salbutamol sulphate/lactose and salbutamol sulphate/PEG were also determined. Spray drying ipratropium bromide monohydrate resulted in a crystalline material from both aqueous and ethanolic solution. The product spray dried from aqueous solution consisted mainly of ipratropium bromide anhydrous. There was evidence of the presence of another polymorphic form of ipratropium bromide. When spray dried from ethanolic solution the physicochemical characterisation suggested the presence of an ipratropium bromide solvate with some anhydrous ipratropium bromide. Co-spray drying salbutamol sulphate with ipratropium bromide resulted in amorphous composites, regardless of solvent used. Particles were spherical and of a size suitable for inhalation. Twin impinger studies showed an increase in the fine particle fraction (FPF) of spray dried salbutamol sulphate compared to micronised salbutamol sulphate. Co-spray dried salbutamol sulphate:ipratropium bromide 10:1 and 5:1 systems also showed an increase in FPF compared to micronised salbutamol sulphate. Most co-spray dried salbutamol sulphate/excipient systems investigated demonstrated FPFs greater than that of micronised drug alone. The exceptions to this were systems containing PEG 4000 20% or PEG 20,000 40% both of which had FPFs not significantly different from micronised salbutamol sulphate. These two systems were crystalline unlike most of the other spray dried composites examined which were amorphous in nature.

Prospects of formulating proteins/peptides as aerosols for pulmonary drug delivery

Formulation of proteins/peptides for therapeutic uses has often posed some challenges to drug formulators. The main problem is the relatively weak forces involved in the native conformation of these proteins and so making them quite labile. Furthermore, their susceptibility to proteolytic enzymes in the gut makes oral administration quite challenging. While various routes like, ocular, transdermal, nasal and buccal have been tried, none of these routes has proved to be a potential alternative to the invasive injection. However, various studies have been performed on the formulation of these proteins as aerosols for pulmonary delivery and promising results have been obtained. This article looks at the prospects of inhaled proteins as a delivery route for systemic activity.

Technologies for laboratory generation of dust from geological materials

Dusts generated in the laboratory from soils and sediments are used to evaluate the emission intensities, composition, and environmental and health impacts of mineral aerosols. Laboratory dust generation is also utilized in other disciplines including process control and occupational hygiene in manufacturing, inhalation toxicology, environmental health and epidemiology, and pharmaceutics. Many widely available and/or easily obtainable laboratory or commercial appliances can be used to generate mineral aerosols, and several distinct classes of dust generators (fluidization devices, dustfall chambers, rotating drums/tubes) are used for geological particulate studies. Dozens of different devices designed to create dust from soils and sediments under controlled laboratory conditions are documented and described in this paper. When choosing a specific instrument, investigators must consider some important caveats: different classes of dust generators characterize different properties (complete collection of a small puff of aerosol versus sampling of a representative portion of a large aerosol cloud) and physical processes (resuspension of deposited dust versus in situ production of dust). The quantity "dustiness" has been used in industrial and environmental health research; though it has been quantified in different ways by different investigators, it should also be applicable to studies of geological aerosol production. Using standardized dust-production devices and definitions of dustiness will improve comparisons between laboratories and instruments: lessons learned from other disciplines can be used to improve laboratory research on the generation of atmospheric dusts from geological sources.

Experimental study of the GAS process for producing microparticles of beclomethasone-17,21-dipropionate suitable for pulmonary delivery

In this study the micronization of beclomethasone-17,21-dipropionate (BECD), used as an inhaled steroid for the treatment of asthma, was studied using the gas-antisolvent (GAS) process as a "green" alternative to pharmaceutical recrystallization. A systematic investigation of the influence of the key GAS process parameters: antisolvent addition rate (1, 50, 75 and 100 ml/min), temperature (25, 32.5, 40 and 52.5 degrees C), solute concentration (5, 25, 70 and 100%), and agitation rate (500, 1000, 2000 and 3000 rpm) were investigated on particle morphology, size distribution, and crystallinity. It was found using scanning electron microscopy (SEM) and laser diffraction, that increasing the antisolvent addition rate and the agitation rate, while decreasing the temperature and solute concentration, led to a decrease in the steroids mean particle diameter. These parameters could be tuned to give a mean particle diameter of 1.8 microm, and an average mass median aerodynamic diameter (MMAD) of 7.9 microm. High-performance liquid chromatography (HPLC) results showed the recrystallized BECD was purer than the non-processed material. The role of the solvent (acetone, methanol and ethanol) in the BECD crystal structure was investigated using X-ray diffraction (XRD), which showed acetone gave a more crystalline structure, hence having lower incorporation into the crystal structure. These results showed that the GAS process has the potential to produce steroid with powder properties suitable for inhalation therapy.

Comparative study of erythritol and lactose monohydrate as carriers for inhalation: atomic force microscopy and in vitro correlation

The adhesion of micronised salbutamol sulphate to two carrier excipients, lactose monohydrate and erythritol, was investigated using the atomic force microscope (AFM) colloid probe technique and correlated with their respective physico-mechanical properties and aerosolisation performance. The particle size, morphology and moisture sorption properties of the carriers were similar thereby allowing direct comparison of functionality. AFM force measurements (n = 1024 force curves) were obtained between salbutamol sulphate drug probes (n = 4) and the excipients, as 63-90 microm sieve fractions and atomically smooth crystals. In general, significant differences in drug adhesion to lactose monohydrate and erythritol were observed (ANOVA, p<0.05), with erythritol exhibiting relatively greater adhesiveness. A linear relationship between drug probe adhesion to lactose monohydrate and drug probe adhesion to erythritol was established with salbutamol sulphate-lactose monohydrate adhesion being 60-70% of that of the erythritol system. In vitro analysis suggested good correlation with the adhesion measurements. The aerosolisation of salbutamol sulphate from erythritol carrier particles was significantly less (ANOVA, p<0.05) than from lactose monohydrate, with a fine particle dose (<6.4 microm) of 41.9 +/- 7.4 microg and 24.9 +/- 3.1 microg for the lactose monohydrate and erythritol carriers, respectively (n = 3).

Artificial Neural Network Prediction of the Patterns of Deposition of Polydisperse Aerosols Within Human Lungs

For optimum therapeutic response from drug administered to the lungs, it is paramount that the aerosolised drug is able to deposit in the lower airways. The filtering characteristics of the respiratory tract, however, make this a particularly challenging task. Computational tools afford a cost-effective means of studying the problem, and here we report on the development of a rapid and reliable method for predicting the pattern of deposition of polydisperse aerosols within human lungs using artificial neural networks (ANNs). Literature (experimental) data on lung deposition of monodisperse aerosols were used to train a single ANN to allow for simultaneous predictions of regional and total aerosol particle deposition patterns in human lungs. When used in modelling the fate of polydisperse aerosols in human lungs, the trained ANN was found to give highly accurate predictions for all lung regions, and all (pharmaceutically relevant) particle sizes and breathing conditions (with errors typically <0.025%). Further testing of the ANN, using 'unseen' in vitro and in vivo data, gave good agreement of lung dosages. It is thus concluded that the ANN produced can be used to provide highly reliable estimates of particle deposition from polydisperse pharmaceutical aerosols generated from breath-actuated dry powder inhalers, nebulizers and metered dose inhalers with spacers.

The effect of water to ethanol feed ratio on physical properties and aerosolization behavior of spray dried cromolyn sodium particles

Cromolyn sodium (CS) was spray dried under constant operation conditions from different water to ethanol feed ratios (50:50-0:100). The spray dried CS samples were characterized for their physicochemical properties including crystallinity, particle size distribution, morphology, density, and water/ethanol content. To determine quantitatively the crystallinity of the powders, an X-ray diffraction (XRD) method was developed using samples with different crystallinity prepared by physical mixing of 100% amorphous and 100% crystalline CS materials. The aerodynamic behavior of the CS samples was determined using an Andersen Cascade Impactor (ACI) with a Spinhaler at an air flow of 60 L/min. Binary mixtures of each spray dried CS powder and Pharmatose 325, a commercial alpha-lactose monohydrate available for DPI formulations, were prepared and in vitro aerosol deposition of the drug from the mixtures was analyzed using ACI to evaluate the effect of carrier on deposition profiles of the spray dried samples. CS spray dried from absolute ethanol exhibited XRD pattern characteristic for crystalline materials and different from patterns of the other samples. The crystallinity of spray dried CS obtained in the presence of water varied from 0% to 28.37%, depending on the ratio of water to ethanol in the feed suspensions. All samples presented different particle size, water/ethanol content, and bulk density values. CS particles spray dried from absolute ethanol presented uniform elongated shape whereas the other samples consisted mainly of particles with irregular shape. Overall, fine particle fraction increased significantly (p < 0.01) with decreasing d50% and water and ethanol content of spray dried CS samples. Significant difference (p < 0.01) in deposition profiles of the drug were observed between corresponding carrier free and carrier blended formulations. The difference in deposition profiles of CS aerosolized from various spray dried samples were described according to the particle size, shape, and water/ethanol contents of the powders. The results of this study indicate that enhanced aerosol performance of CS can be obtained by spray drying of the drug from suspensions containing > or = 87.5% v/v ethanol.

Evaluation of SCF-engineered particle-based lactose blends in passive dry powder inhalers

The objective of this study was to assess the performance of SCF-engineered budesonide and albuterol sulfate powder blends in passive dry powder inhalers (DPI) relative to micronized drug blends. A number of lactose grades for inhalation were screened and the appropriate carrier and drug-to-lactose blending ratio were selected based on drug content and emitted dose uniformity. Aerosol performance was characterized by Andersen cascade impaction. Blend formulations of SEDS (solution enhanced dispersion by supercritical fluids) budesonide and albuterol exhibited a significant drug content uniformity (7-9% RSD) improvement over micronized drug blends (16-20% RSD). Further, the SEDS formulations demonstrated higher emitted dose and reduced emitted dose variability (10-12% RSD) compared to micronized powders (21-25% RSD) in the Turbospin, albeit without significant enhancement of the fine particle fraction. In contrast, SEDS powders exhibited increased fine particle fractions over micronized blends in the Clickhaler; improvements were more pronounced with albuterol sulfate. The performance enhancements observed with the SEDS powders are attributed to their increased surface smoothness and reduced surface energy that are presumed to minimize irreversible drug-carrier particle interactions, thus resulting in more efficient drug detachment from the carrier particle surface during aerosolization. As demonstrated for budesonide and albuterol, SEDS may enhance performance of lactose blends and thus provide an attractive particle engineering option for the development of blend formulations for inhalation delivery.

Formulation development of inhalation powders for FK888 with carrier lactose using Spinhaler and its absorption in healthy volunteers

(4R)-4-Hydroxy-l-[(l-methyl-lH-indol-3-yl)carbonyl]-L-prolyl-N-benzyl-N-methyl-3-(2-naphthyl)-L-alaninamide (FK888) is a candidate selective NK1 receptor antagonist, and it exhibits poor absorption from the gastrointestinal (GI) tract in healthy volunteers. The objective of this study was to develop an optimized DPI formulation with carrier lactose using a Spinhaler, and thereby improve the systemic absorption of FK888. The fine particles of FK888 were blended with various carrier lactoses, and in vitro deposition properties were investigated using a twin impinger. The mixture using 100 M and 325 M lactoses [Sieved lactoses (SLs)] exhibited a higher emitted dose (Em) than 200 M, 450 M and micronized lactoses [Milled lactoses (MLs)]. The flowability of carrier lactose had an influence on the Em. On the other hand, the respirable particle (RP) fraction in the formulations with MLs was much higher than that of SLs, in spite of the blended ratios of lactose. It was also observed that the mixture of 325 M with the micronized lactose particles had the same RP as 200 M, although the 325 M alone had a low RP. Considering the Em and RP obtained, we chose 200 M for FK888 dry powder inhaler (DPI). The proportional absorption was found up to the 12.5% of the FK888 ratio (5 mg as unit dose) for the Cmax and AUC in healthy volunteers. In conclusion, 200 M, which has fine lactose particles and a better flowability than other MLs, is an extremely suitable carrier for maximizing the fine particle dose as far as FK888 is concerned. Furthermore, an improvement in the systemic absorption of FK888 was achieved using the dry powder formulations.

Stability of chitosan–pDNA complex powder prepared by supercritical carbon dioxide process

The present study examined the stability of a gene in powders prepared with supercritical carbon dioxide (CO(2)) from the viewpoints of the ternary structure of DNA and in vivo transfection potential. An aqueous chitosan-pCMV-Luc complex solution containing mannitol was injected into the stream of a supercritical CO(2)/ethanol admixture to precipitate a gene powder. The obtained gene powders and gene solutions were placed in stability chambers at 25 or 40 degrees C for 4 weeks. The integrity and transfection potency of the gene were examined by electrophoresis and in vivo pulmonary transfection study in mice. The supercritical CO(2) process decreased the supercoiled DNA during the manufacturing process; however, the decrease in the remaining supercoiled and open circular DNA in the powders during storage was much slower than that in solutions. In addition, the powders had higher transfection potency than the solutions containing the same amount of DNA. The effect of chitosan on the stability of DNA in solutions was not obvious in the solutions but it improved the stability of DNA in powders during manufacturing and storage. Thus, a gene powder with a cationic vector is a promising ready-to-use formulation for inhalation therapy of pulmonary diseases.

Optimized dose delivery of the peptide cyclosporine using hydrofluoroalkane-based metered dose inhalers

The goal of this study was to illustrate the potential to deliver relatively high doses of a therapeutic peptide using hydrofluoroalkane (HFA) metered dose inhaler (MDI) drug delivery systems. For the purposes of this study, cyclosporine was used as the model compound. Cyclosporine formulations, varying in peptide concentration, ethanol cosolvent concentration, and propellant type, were evaluated and optimized for product performance. As ethanol concentration was decreased from 10 to 3% by weight, fine particle fraction (the mass of cyclosporine which passes through a 4.7-micron cut point divided by the total mass of cyclosporine delivered ex-valve) increased from 34 to 68% for 227 and 33 to 52% for 134a formulations. Because of the excellent solubility properties of cyclosporine in HFA-based systems, minimal or no ethanol was needed as a cosolvent to achieve cyclosporine concentrations of 1.5% w/w. With these formulations, it was possible to obtain a fine particle mass (mass of particles <4.7 microns) greater than 500 microg per actuation. In addition, one formulation was chosen for stability analysis: 0.09% w/w cyclosporine, 10% w/w ethanol, 134a. Three different types of container closure systems (stainless steel, aluminum, and epoxy-coated canisters) and two storage configurations (upright and inverted) were evaluated. Cyclosporine was determined to be stable in HFA 134a-based MDI systems, regardless of container closure system and configuration, over a 2-year period. Cyclosporine represents a compelling example of how significant peptide doses are attainable through the use of solution-based MDIs. It has been shown that through formulation optimization, 2-3 mg of the peptide, cyclosporine, may be delivered in five actuations to the lung for local or systemic therapy.

Aerosolisation of beclomethasone dipropionate using spray dried lactose/polyethylene glycol carriers

The aim of this study was to characterize the physical properties of spray dried lactose in the presence of different polyethylene glycols (PEG 400, PEG 3000 and PEG 6000) and to evaluate their performance as carriers for dry powder inhaler (DPI) formulations. The efficiency of spray dried lactose/PEG carriers in aerosolisation of beclomethasone dipropionate (BD), a model hydrophobic drug, was compared to Pharmatose 325 M (L325), spray dried lactose alone (SDL), and also a sieved (< 38 microm) fraction of alpha-lactose monohydrate (SL). In vitro deposition analysis was performed using a twin stage liquid impinger at a flow rate of 60 l/min through a Spinhaler. The deposition profiles of the drug from binary formulations composed of BD and spray dried lactose/PEG carriers were also compared to ternary formulations containing large and fine lactose carriers. Differential scanning calorimetry and X-ray diffraction data showed the presence of alpha-anhydrous lactose in spray dried lactose/PEG crystalline powders. Spray drying of lactose in the presence of PEG 400 resulted in the production of a powder (SDL-PEG400) with lower alpha-lactose monohydrate content, and also smaller particle size distribution than those obtained in the presence of PEG 3000 (SDL-PEG3000) or PEG 6000 (SDL-PEG6000). All formulations showed different deposition profiles, except those containing SDL-PEG3000 or SDL-PEG6000 which exhibited similar data. The fine particle fraction of aerosolised BD varied from 6.26 +/- 1.07 (for L325) to 25.87 +/- 5.33 (for SDL-PEG3000). All deposition profiles of BD aerosolised from SDL-PEG3000 were significantly higher (P < 0.01) than those produced by binary and ternary formulations containing L325, a coarse lactose commercially available for DPI formulations. The differences observed in deposition data for various carriers were interpreted according to their physical properties. It was concluded that particle size distribution, morphology and specific surface texture of SDL-PEG3000 and SDL-PEG6000 were important factors influencing their efficiency as small carriers for DPI formulations.

Aerosolization properties, surface composition and physical state of spray-dried protein powders

Powder aerosols made of albumin, dipalmitoylphosphatidylcholine (DPPC) and a protein stabilizer (lactose, trehalose or mannitol) were prepared by spray-drying and analyzed for aerodynamic behavior, surface composition and physical state. The powders exited a Spinhaler inhaler as particle aggregates, the size of which depending on composition, spray-drying parameters and airflow rate. However, due to low bulk powder tap density (<0.15 g/cm3), the aerodynamic size of a large fraction of aggregates remained respirable (<5 microm). Fine particle fractions ranged between 21% and 41% in an Andersen cascade impactor operated at 28.3 l/min, with mannitol and lactose providing the most cohesive and free-flowing powders, respectively. Particle surface analysis by X-ray photoelectron spectroscopy (XPS) revealed a surface enrichment with DPPC relative to albumin for powders prepared under certain spray-drying conditions. DPPC self-organized in a gel phase in the particle and no sugar or mannitol crystals were detected by X-ray diffraction. Water sorption isotherms showed that albumin protected lactose from moisture-induced crystallization. In conclusion, a proper combination of composition and spray-drying parameters allowed to obtain dry powders with elevated fine particle fractions (FPFs) and a physical environment favorable to protein stability.

Micron-size drug particles: common and novel micronization techniques

Drug powders containing micron-size drug particles are used in several pharmaceutical dosage forms. Many drugs, especially newly developed substances, are poorly water soluble, which limits their oral bioavailability. The dissolution rate can be enhanced by using micronized drugs. Small drug particles are also required in administration forms, which require the drug in micron-size size due to geometric reasons in the organ to be targeted (e.g., drugs for pulmonary use). The common technique for the preparation of micron-size drugs is the mechanical comminution (e.g., by crushing, grinding, and milling) of previously formed larger particles. In spite of the widespread use of this technique, the milling process does not represent the ideal way for the production of small particles because drug substance properties and surface properties are altered in a mainly uncontrolled manner. Thus, techniques that prepare the drug directly in the required particle size are of interest. Because physicochemical drug powder properties are decisive for the manufacturing of a dosage form and for therapeutic success, the characterization of the particle surface and powder properties plays an important role. This article summarizes common and novel techniques for the production of a drug in small particle size. The properties of the resulting products that are obtained by different techniques are characterized and compared.

Improvement of stability and absorbability of dry insulin powder for inhalation by powder-combination technique

The effect of pulmonary absorption enhancers on the stability of active ingredients is an important factor for successful inhalation therapy as well as the effect on pharmacological activity and safety. We examined the effect of pulmonary absorption enhancers on the stability of insulin in dry powders prepared by a spray-drying technique. Although the hypoglycemic effect was greatly improved when a dry insulin powder containing citric acid (MIC SD) was administered, insulin in the MIC SD was unstable compared with the other powders examined. Bacitracin and Span 85, which are potent pulmonary absorption enhancers of insulin formulated in solutions, showed no deteriorative effect on the stability of dry insulin powder. However, they did not improve the hypoglycemic effect of insulin in dry powders. We modified the insulin dosage form with citric acid to improve the insulin stability at room temperature without loss of hypoglycemic activity. MIC Mix was formulated as a combination of insulin powder (MI') and citric acid powder (MC). MIC Mix showed hypoglycemic activity comparable to MIC SD while the insulin stability was much better than that of MIC SD at a 60 degrees C/dry condition. However, moisture lowered the insulin stability and changed the particle morphology of MIC Mix with time at a 60 degrees C/75% relative humidity condition, suggesting that a package preventing moisture absorption was necessary for the MIC Mix powder.